All language subtitles for S10E10 - Bronze Bells; Wooden Airplane Propellers; Charcoal Briquettes; Gas Log Fireplaces (1080p AMZN WEB-DL x265 Garshasp)_track3_[eng]

Narrator:
Today on "How it's made"...

Bronze bells...

...Wooden airplane propellers...

...Charcoal briquettes...

...And gas-log fireplaces.

Throughout history,

Bells have played both practical
And ceremonial roles.

Village bells would ring
To mark time

And to warn of danger.

Church bells would toll
To summon worshipers.

Bells are traditionally cast
Of bronze,

A metal that's as durable
As it is melodic.

[ bells tolling ]

When it comes to bell making,

There'd be neither swing
Nor ring without a mold.

And only a quality mold
Makes a quality bell.

The mold is made
Using a pattern.

This particular bell will have
Decorative lines on the surface,

Which will require
A separate mold

Made from this
Five-piece pattern.

After greasing the pattern's
Surface with a release agent,

Workers lower a wooden casing
Around it.

This casing
Will hold the mixture

Of fine silica sand and epoxy
They'll use to make the mold.

Workers pack the material
Tightly

Between the pattern and casing.

The epoxy sets in 10 minutes,

And now they have a sand mold

In which to cast
The bell's decorations.

They still need a mold
To cast the bell itself.

They make it
With this aluminum pattern.

After spraying it inside and out
With a release agent,

They lower the decoration mold
They just made right over it...

Then on top of that, a steel
Casing to contain the sand mix.

Workers pack the sand mix
And wait for it to set.

Then they flip the casing
And add another section

To hold even more sand mix.

But before the next load
Of sand,

They insert what's called
The gate.

This aluminum rod
Shapes the channel

Through which they'll pour
The molten bronze

Into the mold cavity.

They fill up the mold
With more sand.

Then they form a funnel
Around the central channel

Because
It's virtually impossible

To pour molten bronze directly
Into such a small hole.

They poke the sand mix
To make sure it's set,

Then pull out the gate.

They separate the two casings,

Each of which contains
A section of the mold.

Then the patterns come out,
Leaving behind the mold cavity.

Workers tidy up the mold walls

And paint on
A powdered graphite solution

Which will act as a barrier,

Preventing the hot metal
From eroding the epoxy

That holds the sand mold
Together.

Next, they spray on
A second coat of wash.

The sand is so fine
That without this step,

The mold would reproduce
The brush strokes

Onto the cast bell.

Now they measure the size
Of the pour hole

And custom-make a ceramic filter
To glue inside.

This filter will screen out
The slag,

Oxidized particles that form
When molten metal meets air.

Workers stack the two mold
Sections back together

And clamp them tightly so that
The bronze won't leak out

During casting.

Melting enough bronze ingots
For an average-size bell

Takes about two hours.

To get a smooth enough
Consistency,

The furnace has to heat the
Metal to about 2,100 degrees.

For a quality casting,

They must pour the bronze
In one continuous flow --

No stops and starts.

The funneling basin they made in
The sand prevents overflowing.

The bronze takes about
A half-hour to solidify

And up to 24 hours to cool.

Workers remove the sand mold
With a jackhammer,

Being very careful not to hit
The bell inside.

The extracted bell is covered
In a residue of burnt epoxy,

Which they remove
With a wire brush.

Then, with one well-aimed strike
Of a sledgehammer,

They disengage the gate.

Now they mark the exact
Center point of the bell.

That's where they'll install
The hardware

From which the bell will hang.

They drill a small hole,

Then gradually drill it larger
And larger.

A big hole can't be bored
In one shot

Because the friction-induced
Heat would crack the bell.

Workers tip the bell on its side
To hang the clapper --

The official name
For the bronze hammer inside.

Every bell this factory produces

Goes through six stages
Of polishing,

Starting with
A coarse grinding belt

And finishing with
A fine-cloth buffing wheel.

Two hours of polishing later,

The bell looks as beautiful
As it sounds.

[ bells tolling ]

Coming up...A new spin
On a centuries-old invention --

The wooden propeller.

Narrator: the propeller
Dates back to 1493,

When leonardo da vinci
Sketched out

The concept for a helical screw

That could propel a machine
Vertically into the sky.

The propeller is still
Occasionally referred to

As an airscrew --

A term that accurately reflects
Its basic design and function.

The key to making one --
Plenty of sanding.

Wooden propellers start out as
A laminated block of maple wood.

Lamination is a process

Where several layers
Are glued together.

The block
Has between 36 and 48 layers

Less than 1/16 of an inch thick.

Depending on the model,
Workers select a master pattern

That is between one
And two yards long.

They lay this pattern
Over the maple block

And mark a one-inch center hole.

They drill the hole...

And lay in a centering pin
To hold the pattern in place.

A worker traces the pattern
On the top of the block.

He then cuts the outline
With a band saw.

This is the propeller's profile.

Next, he traces a pattern
On the side of the block.

This is the propeller's pitch --

The amount of twist
In the blades,

Which dictates the amount
Of propeller thrust.

Using a pattern guide,

He marks where the pitch
Blends into the center hub,

Then removes the bulk
Of the pitch with a band saw.

Now he clamps the block onto a
Computer-guided milling machine

That carves the pitch
To very precise dimensions.

The machine's
Carbide-tipped cutters

Shave infinitesimal amounts
Of wood with each pass.

Precision milling
Just one end of the propeller

Can take up to 60 passes.

Next, a worker shapes
The airfoil with a band saw.

The airfoil is the side
Of the propeller

That is shaped
Like an airplane wing

And produces forward thrust.

The pitch side...

And the airfoil side.

Workers use a tool
Called a spokeshave

To smooth the propeller
Even more.

Then they verify the airfoil's
Thickness and curve

With a hand gauge.

A spray of dark paint helps them
Know where they've been

As they begin smoothing
The propeller's surface.

They remove any remaining
Carving marks

Using a belt sander.

Then they check the propeller
For balance.

Using a pneumatic sanding drum,

They perform an overall sanding

And punch in propeller
Specifications --

Diameter, pitch,
Flight direction symbols,

And manufacturer I.D.

Workers hand-inspect
The propeller,

Then perform a final sanding
And balance.

A coat of clear enamel
Seals the wood.

And a safety color
Sprayed on the tips

Makes the propeller visible
While it's spinning.

Two final protective coats
Of clear enamel,

24 hours of drying time,

And these propellers
Are ready for takeoff.

When we return,
Fire up the grill.

It's time to make
Some charcoal briquettes.

Narrator: the charcoal briquette
Was invented in 1897,

But interest in it was
Slow-burning, so to speak,

Until the 1920s.

That's when automaker henry ford

Decided to recycle wood scraps
From car making

Into barbecue briquettes,

And these little nuggets
Became a smoking sensation.

Barbecuing with charcoal

Has become immensely popular
Since ford's time,

And every year, several
Million tons of wood scraps

Are converted into high-quality
Charcoal briquettes.

Today, briquette production

Starts with sawdust and
Wood chips from lumber mills.

A truck unloads it all
Into a pit.

Bulldozers blend the material
Called fuel

To obtain a uniform end product.

As the mix travels up
A conveyer,

An electromagnet removes
Any metal contaminates.

The mix falls onto
A vibratory screener,

Which sifts out
The larger pieces of wood.

At this point,
The fuel is still very moist.

To dry it,
A worm screw draws the mix

Up into a long, rotating dryer.

The dryer heats the wood mix
To a searing 1,400 degrees.

The dryer is sealed to prevent
Oxygen from leaking in.

This allows the wood
To dry without catching fire.

After four minutes in the dryer,

The moisture has been cooked out
Of the mix.

Workers add anthracite coal
To the hopper,

And it mixes in with the fuel.

Anthracite coal is known
For burning at high temperature.

Then they mix in lime.

Lime makes the briquettes turn
White after they're ignited --

A visual indication
That the barbecue

Is ready to rock 'n' roll.

The mix, now blackened, passes
Under a second electromagnet

To remove any metal that could
Damage the equipment downstream.

Finally, workers blend in
Cornstarch,

Which binds
The ingredients together.

A worm screw supplies
The mixture to a press roll,

Where a constant spray of water
Keeps the mixture from sticking.

The press rolls compact
The mixture into briquettes.

The process takes
Just a fraction of a second.

At this point, the briquettes
Contain 35% moisture

And are very soft.

A screener shakes out fine
Material from the briquettes,

Which is recycled
Back into the process.

A sweep belt transports
And distributes the briquettes

In a 250-foot drying tunnel.

They are heated to 280 degrees
For 2 1/2 hours.

This will reduce their moisture
Level from 35% to just 5%.

The lower the moisture level,
The better it burns.

A conveyer transports the
Briquettes to automated scales

That weigh them for packaging.

Every portion is the same,
Plus or minus one briquette.

As the scales
Release the briquettes,

Robots below move bags
Into position to capture them.

A sealing machine
Glue-seals the bags,

Then prints a production date
And shipped code on each one.

Open the bag,
And a backyard barbecue

Is just one match stroke away.

And who can resist the smokey
Flavor of charcoal-grilled food?

When we return...Turning up
A different kind of flame

With gas-log fireplaces.

Narrator: gas-log fireplaces
Are clean-burning,

Fully contained units
That are growing in popularity.

They provide instant warmth
At the flick of a switch.

And you'll never have to head
Out on a cold winter night

To get more logs
Or clean up the ashes.

To make a gas-log fireplace,

Workers first screw fittings
To a gas-control valve.

Then they attach the valve
And gas pilot to the frame.

The gas pilot is a small flame
That burns continuously,

Enabling you to ignite the gas
Instantly.

They cap the control valve
With knob extensions

That allow the user to control
The flame's intensity

From outside the fireplace.

Next, they install burners
And orifices.

The orifice controls the gas
Flow in each of the burners.

They attach an electrical
Connection from the gas pilot

To the control valve...

Adjust the length of
The gas-pilot supply line...

And screw the line
To the control valve.

Finally, the line is attached
To the gas pilot.

The fireplace's ignition system
Is now complete.

Next, workers attach a safety
Device called a thermocouple

To the control valve.

If the flame ever goes out,

The thermocouple
Cuts the gas supply.

The unit now undergoes testing

To ensure that there are
No leaks.

What's a fireplace without logs,

Even if they're replicas
Of the real thing?

This factory
Makes artificial logs

From a mixture
Of fire-resistant ceramic fibers

And a liquid resin
That binds the fibers together.

Workers attach a log-forming
Mold to a pumping arm...

Then immerse the arm
In the mixture.

The mixture
Fills the mold cavity.

The mixture is soft
When it comes out of the mold

And is held together

By the dense, interwoven layers
Of fibers.

The excess fiber is trimmed off,

And the log is placed
On a baking rack.

Then it's into an oven
At 450 degrees for 5 hours.

When it comes out,
It's as hard as a log.

Workers remove the sharp edges
With a rasp,

Then dip the log in a mixture of
Binder and heat-resistant paint.

Over that,
They hand-paint details

Replicating the look
Of charred wood.

The paint is baked on, making
This decoration permanent.

And it'll have no problem
Taking the heat.

The paint
Can withstand temperatures

Up to 2,300 degrees.

Back in the testing department,
Workers calibrate the mechanism

That adjusts
The fireplace flame.

They use a flowmeter to verify
The rate at which the gas flows.

The back burner produces
A yellow flame,

While the front burner
Gives off a reddish glow.

Combined,
They look more realistic.

Workers package
The individual components

And include some lava rock

To simulate a bed of ashes
Underneath the logs.

It all adds up to a beautiful,
Cozy fire...

At the flick of a switch.

--captions by vitac--
Www.Vitac.Com

Captions paid for by
Discovery communications, llc

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